Articles | Volume 14, issue 18
Research article
15 Sep 2017
Research article |  | 15 Sep 2017

Source, composition, and environmental implication of neutral carbohydrates in sediment cores of subtropical reservoirs, South China

Dandan Duan, Dainan Zhang, Yu Yang, Jingfu Wang, Jing'an Chen, and Yong Ran

Abstract. Neutral monosaccharides, algal organic matter (AOM), and carbon stable isotope ratios in three sediment cores of various trophic reservoirs in South China were determined by high-performance anion-exchange chromatography, Rock-Eval pyrolysis, and Finnigan Delta Plus XL mass spectrometry, respectively. The carbon isotopic compositions were corrected for the Suess effect. The concentrations of total neutral carbohydrates (TCHO) range from 0.51 to 6.4 mg g−1 at mesotrophic reservoirs, and from 0.83 to 2.56 mg g−1 at an oligotrophic reservoir. Monosaccharide compositions and diagnostic parameters indicate a predominant contribution of phytoplankton in each of the three cores, which is consistent with the results inferred from the corrected carbon isotopic data and C∕N ratios. The sedimentary neutral carbohydrates are likely to be structural polysaccharides and/or preserved in sediment minerals, which are resistant to degradation in the sediments. Moreover, the monosaccharide contents are highly related to the carbon isotopic data, algal productivity estimated from the hydrogen index, and increasing mean air temperature during the past 60 years. The nutrient input, however, is not a key factor affecting the primary productivity in the three reservoirs. The above evidence demonstrates that some of the resistant monosaccharides have been significantly elevated by climate change, even in low-latitude regions.

Short summary
Neutral carbohydrates, carbon isotopic composition, and algal productivity proxies in three reservoir sediment cores, South China, were investigated. Monosaccharide compositions and diagnostic parameters indicate a predominant contribution of phytoplankton in the sediment cores. Algal monosaccharide content is highly related to the algal productivity and increasing mean air temperature, but not to nutrient input, demonstrating the effect of climate warming in low-latitude regions.
Final-revised paper